It is known in the art to encode by pulse position modulation an LPOS word comprising 36 bits of information in a non-data region of a sequential data storage medium, such as a magnetic tape. Each encoded LPOS word relates to a specific absolute longitudinal address, and appears every 7.2 mm down the tape. Using prior art methods, an LPOS word comprises 36 individual servo patterns, i.e. frames, wherein each frame encodes one bit of information. The LPOS values of two consecutive LPOS words differ by one. Therefore, a tape drive can position a data/servo head assembly at a specified LPOS address thereby achieving a longitudinal resolution of about 7.2 mm.
A read/write assembly comprising two servo heads spans a data band and two servo bands disposed adjacent that data band. In the event one servo head is rendered inoperative, then only one servo head can be used to laterally position the read/write head. Alternatively, a servo band may become damaged, or may not comprise useful information resulting from media damage.